Theanine is an amino acid primarily found in green tea (Camellia sinesis) and produced by an enzyme reaction of L-glutamine and ethylamine. Generally, theanine takes about 1 to 2 wt. % with respect to the total dry weight of green tea leaves and exists primarily in the form of free amino acid. It is reported that theanine suppresses the stimulant action of caffeine (Toxicol Lett. 2001 123(2-3), 159-167, Biosci. Biotechnol. Biochem. 2000 February; 64(2):287-93), increases alpha-waves in the brain to alleviate the stress (Nippon Nogeikagaku Kaishi 1998; 72:153-157) and has an anti-stress effect, such as inhibiting the increase in the cardiac impulses caused by the stress and reducing the factors on the stress reaction (Bio Psychol. 2007 74(1):39-45). Theanine is also reported to have a cancer-fighting action by reducing the level of glutathione in the cancer cells (Cancer Lett. 2004 212(2), 177-184), drop the blood pressure (Biosci Biotechnol Biochem 1995 59(4) 615-618) and partly exert an antioxidant function of inhibiting the oxidization of low-density lipoprotein cholesterol (LDL-cholesterol) (Exp Toxicol Pathol 1997; 49:329-335). Recently, some studies have been made on the physiological activities of theanine, such as having an anti-obesity function (In Vivo 2004, 18(1) 55-62) and increasing levels of enzymes participating in alcoholysis.
The probability that theanine has various physiological activities has been investigated and specifically studied. But, what it comes to the dermatological region, there have never been reported any known studies or reports on the dermatological efficacies of theanine and their related mechanisms, except for the activities of theanine and catechin, an ingredient of green tea, when used alone or in combination, such as breaking down fat (Korean Laid-open Patent Publication No. 2004-0092538), improving skin aging (Korean Laid-open Patent Publication No. 2007-0028901) and promoting proline recycling (Korean Laid-open Patent Publication No. 2009-0064743). US2006/0134095 A1 discloses the moisturizing effect of theanine and the theanine derivative as a cell activator. But, not much is known about the excellent dermatological efficacies of theanine derivatives other than theanine.